The present invention relates to a method for manufacturing a high-pressure phase material, in particular, to a method for manufacturing high-pressure phase boron nitride and diamond by using shock compression.
Japanese Patent Publication Nos. Showa 47-34597 and 52-4511 disclose methods for manufacturing high-pressure phase boron nitride and diamond. In the conventional methods, high-pressure phase product (diamond) was manufactured from low-pressure phase starting material (graphite) by using a shock pressure produced by explosion of explosive or by the collision caused by accelerated flyer.
Rapid quenching of the high-pressure phase product is essential in the conventional manufacturing methods. The low-pressure phase starting materials, such as graphite and boron nitride, are compressed by a shock wave to elevate the temperature, which transfers the phase into the high-pressure phase, such as high-pressure phase boron nitride and diamond. However, the duration of the state having the elevated temperature and the high pressure, obtained by the shock wave, is extremely short, like as between several micro-seconds and several tens of micro-seconds, and the pressure immediately drops to the atmospheric pressure. On the other hand, the heat generated by the shock pressure remains on the high-pressure phase product, even after the pressure has dropped. Accordingly, the high-pressure phase boron nitride and diamond undergo reverse phase transition. This decreases the conversion rate from the low-pressure phase starting material to the high-pressure phase product.
Accordingly, in order to increase the conversion rate towards the high-pressure phase product, a mixture of the low-pressure phase starting material powder and a metal powder (quenching medium) having large heat capacitance and high thermal conductivity is used. Metal powders, such as gold, platinum, silver, copper, iron, nickel and tungsten, are used as the quenching medium. The high-pressure phase product is manufactured through shock compression of the low-pressure phase starting material that is dispersed in the quenching medium matrix.
The metal powder acts as the quenching medium, and at the same time as the pressure medium. In the case where only the low-pressure phase starting material is compressed, without mixing the metal powder, the pressure applied to the low-pressure phase starting material is insufficient because the shock impedance is relatively low. Given that sufficient pressure is applied to the low-pressure phase starting material, the temperature of the low-pressure phase starting material becomes extremely high under the shock pressure. Because this increases the residual temperature on the low-pressure phase starting material, the conversion rate from the low-pressure phase starting material to the high-pressure phase product is reduced.
By mixing the powder of the low-pressure phase starting material and matrix metal having relatively high shock impedance, the shock impedance of the mixture is improved. As a result, sufficiently high pressure is applied to the low-pressure phase starting material. In addition, the residual temperature on the low-pressure phase starting material is decreased by the quenching effect of the matrix metal.
The powders of the high-pressure phase products (such as high-pressure phase boron nitride and diamond), which are manufactured through these conventional methods, are used in manufacture of: boron nitride cutting tool, and precision grinding processes of the semiconductor products, and components of precision machinery products. However, impurities in the high-pressure phase product powder can mix into the precision ground components in the precision grinding process. Such contamination by the impurities in the high-pressure phase product powder can cause adverse effects on the performance of the semiconductor products and the precision machinery products. Accordingly, grinding materials having high purity, which contains least possible impurity, are needed. However, it is difficult to remove the impurities from the high-pressure phase products in the purification process after shock pressurizing.
An object of the invention is to provide a method for manufacturing highly purified high-pressure phase products.
To achieve the above object, the present invention provides a method for manufacturing a high-pressure phase product. The method includes mixing a metal powder and a low-pressure phase starting material, forming a block by pressurizing the mixture of the metal powder and the low-pressure phase starting material, and shock-compressing the block. The metal powder has a purity of 99.8% or more and has a maximum concentration of any acid-insoluble impurity of 50 ppm or less.
Another perspective of the present invention is a method for manufacturing a high-pressure phase product by using shock compression. The method includes uniformly mixing a low-pressure phase starting material and a matrix metal powder having a purity of 99.8% or more and having a maximum concentration of any acid-insoluble impurity of 50 ppm or less, compressing the mixture of the matrix metal powder and the low-pressure phase starting material so as to make the porosity between 5 and 50%, containing the mixture and an explosive in a container, transferring the phase of the low-pressure phase starting material into high-pressure phase by exerting the shock pressure to the raw material mixture by detonating the explosive in the container, and purifying the phase-transferred product.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.